There's a very good reason why the premium costs are in the rules.
If you want more tactical nuance regarding isssue track play (and, for that matter, advertising), I suggest you use the popular Dunnagan variant (i.e. no cube placement allowed on the issue shown on the card used for that issue positioning action).
Without you stating what those very good reasons are I find it difficult to respond to your statement. So far through our games we have yet to see a problem. Struggles over issues were dynamic and freewheeling and media was a strong way to counter an advantage a player had in issues. While the issues cubes go up to five at times, there are also times in the game where they completely blank out. So far we much prefer this method of being able to place issue support where we want it.
I find the Dunnagan variant adds extra unneeded complexity and restricts tactical choices. The low cost variant maintains free choice similar to what makes the campaigning so nice, the player gets to decide where to put resources in the context of the electoral map. In the context of issue importance, why arbitrarily restrict players on where they place influence? The premium rule forces the efficient minded player to play 3CP cards playing evenly across the issues. In response the other player matches creating a boring add/remove cycle. The Dunnagan variant simply adds more restrictions rather than removes the restrictions that causes the problem in the first place.
I just prefer the free choice of the "low cost" variant versus adding arbitrary restriction onto arbitrary restriction.